Positive displacement pump

Abstract: The pump has a rotor (18) riding on a shaft end (12-3) and is eccentric with respect to the rotational axis of the shaft (12). The rotor (18) rotates in a bore (16-2) of a pivot ring (16) and coacts therewith in the nature of a double action pump such that there are two pumping cycles per revolution of the shaft (12).

Description: Fluid machines such as compressors are typically lubricated by oil drawn from a sump by a pumping structure associated with the crankshaft. Centrifugal pumps and positive displacement pumps such as gerotors are commonly used to pump the oil. One problem associated with some rotary compressors such as scroll compressors is that they can run in reverse due to miswiring or due to a pressure equalization across the compressor upon shut down. Under these conditions some types of oil pumps do not function properly and damage can result from lack of adequate lubrication. Those oil pumps that do function properly under reverse rotation conditions are, typically, relatively complicated and costly. A positive displacement pump as defined in the precharacterizing portion of independent claim 1 is disclosed in US-A-2,260,868 which concerns a combined lubricating oil supply pump and air pump for supplying air to a fluid operated wiper motor. A similar pump is also disclosed in US-A-2,260,867. When the direction of rotation changes the fluid flow direction through the pumps disclosed in US-A-2,260,868 and US-A-2,260,867 reverses. It is an object of this invention to provide a positive displacement oil pump having few parts, low cost and high reliability, suitable for horizontal and vertical orientation, and which pumps fluid in one direction independent of the direction of shaft rotation. To achieve this there is provided in accordance with the invention a positive displacement pump for a fluid machine having an oil supply comprising a shaft having a rotational axis; oil supply and distribution means; rotor means drivingly received on said shaft and located eccentrically with respect to said rotational axis; means defining a cylinder having a bore defined by a pair of semicircular portions joined by straight sections corresponding in extent to a distance by which said rotor means is located eccentrically with respect to said rotational axis, said bore receiving said rotor means and coacting therewith to define at least one trapped volume; oil passage means in said rotor means coacting with said oil supply and distribution means to supply cil from said oil supply to said trapped volume during a suction stroke and from said trapped volume to said oil distribution means during a discharge stroke; characterized in that said oil supply and distribution means are formed in said shaft, and said shaft has a limited relative rotational movement with respect to said rotor means and said means for supplying oil and said means for delivering oil each including a pair of alternative flow paths whereby said pair of alternative flow paths for supplying oil from said oil supply to said trapped volume during a suction stroke and said pair of alternative flow paths for supplying oil from said trapped volume to said oil distribution means during a discharge stroke reverse function between paths of said pairs of alternative paths upon reverse rotation of said shaft. In one embodiment, the eccentric rotor is received on a shaft end and surrounded by a pivot ring which pivots about a fixed point. An end cap coacts with the shaft end to hold the rotor and pivot ring in place. A pin fixed in the shaft end coacts with a slot in the rotor to position the rotor in accordance with the direction of rotation of the shaft. For either direction of rotation, the pin coacting with the slot causes the eccentric rotor to be properly positioned relative to the fluid passages to permit pumping of oil in one direction. An exemplary embodiment of the positive displacement pump will now be described with reference to the accompanying drawings, wherein: Figure 1 is a side view of the shaft end; Figure 2 is an end view of the shaft end of Figure 1; Figure 3 is a sectional view taken along 3-3 of Figure 2; Figure 4 is an end view of the pivot ring; Figure 5 is an end view of the eccentric rotor; Figure 6 is a sectional view taken along 6-6 of Figure 5; Figure 7 is an end view of the end cap; Figure 8 is a sectional view of the assembly; Figures 9 A-D are sectional views taken along line 9-9 of Figure 8 at 90° intervals of the rotation of the shaft with Figure 9A corresponding exactly to Figure 8; and Figure 10 represents a position corresponding generally to that of Figure 9C under conditions of reverse rotation. In the Figures, the numeral 12 generally designates the shaft of a fluid machine such as a scroll compressor. As best shown in Figures 1-3, shaft 12 has a first portion 12-1 and a cylindrical, reduced diameter shaft end 12-3 separated from the first portion by shoulder 12-2. Drive pin 14 is received in a bore in shaft 12 and axially extends from shoulder 12-2. Axially extending grooves 12-4 and 12-5 are formed in the surface of shaft end 12-3 and form part of the oil feed structure. Bore 12-6, which has a threaded portion 12-7, is supplied by the pump structure via radial passage 12-8 or 12-9, depending upon the direction of rotation of shaft 12, and supplies oil to the bearings etc. (not illustrated) requiring lubrication. A-A is the axis of bore 12-6 and shaft 12. Referring now to Figure 4, the numeral 16 designates the pivot ring. Pivot ring 16 has a bore 16-1 with an axis, appearing as point B, about which pivot ring 16 pivots. Pivot ring 16 has a second bore 16-2 which is made up of two 180 semi-circular portions centered on axes represented by points C and D, respectively,and joined by two straight segments equal to the separation of C and D. As best shown in Figures 5 and 6, eccentric rotor 18 has an outer cylindrical surface 18-1 centered on E and of a diameter nearly equal to that of the semi circular portions of bore 16-2 whereby rotor 18 is received in bore 16-2 with a slip fit and with sealing contact. Circular bore 18-2 is formed in rotor 18 and has a center F which is spaced from E the same distance as the spacing of C and D. Rotor 18 has a diametrical bore, intersecting bore 18-2, made up of two segments, 18-3 and 18-4, respectively. Arcuate slot 18-5 is formed in rotor 18 and receives drive pin 14. As best shown in Figure 7, end cap 20 has a central bore 20-1 and two bores, 20-2 and 20-3, which register with grooves 12-4 and 12-5, respectively. The assembled pump assembly 10 is best shown in Figures 8 and 9A. Shaft end 12-3 is surrounded by rotor 18 which is received in bore 16-2 of pivot ring 16 such that drive pin 14 is located in slot 18-5 and bore 16-2 acts as a cylinder or piston chamber for rotor 18 which acts as a piston. Pivoted ring 16 is suitably pivotably secured to a pump end bearing, or the like 22 as by bolt 24. Alternatively, a pin pressed into bearing 22 with a slip fit and extending into bore 16-1 may provide a pivot for ring 16. End cap 20 is properly located with respect to shaft 12, as by dowel pins or assembly fixtures (not illustrated) such that bores 20-2 and 20-3 register with grooves 12-4 and 12-5, respectively. Bolt 26 is received in bore 20-1 and threaded into threaded portion 12-7 of bore 12-6 such that rotor 18 and pivot ring 16 are secured between shoulder 12-2 and end cap 20 and coact to define the suction and discharge chambers. Thus, rotor 18, which rides on shaft end 12-3, is made eccentric with respect to the rotational axis, A-A, of shaft 12. This can be accomplished by offsetting the axis, F-F, of the bore 18-2 in rotor 18, from axis E-E, as illustrated, or by making the shaft end 12-3 on which it rides eccentric to axis A-A of shaft 12 by the same amount. Shaft 12 is machined such that shaft end 12-3 slip fits into the bore 18-2 of rotor 18. Shoulder 12-2 should be larger than the diameter of bore 16-2 of pivot ring 16 to seal off the shaft side of pump assembly 10. If it is not, a suitable ring, or the like, would be affixed to shaft 12 to provide this seal. Pivot ring 16 pivots on bolt 24 which is rigidly affixed relative to the pump housing. Ring 16 must be free to pivot due to the eccentricity of the rotor 18. Alternatively, ring 16 could be flat on two opposite outer sides and reciprocate inside a housing rather than pivoting, as is the case with a slider block. In Figure 8, which corresponds to Figure 9A, oil from sump 30 passes via bore 20-3, groove 12-5 and bore 18-4 into chamber 32 which is functioning as a suction chamber. Oil in chamber 34, which is functioning as a discharge chamber, is pumped via bore 18-3 and bore 12-8 into bore 12-6 from which it passes to the bearings, etc. requiring lubrication. Referring now to Figures 9 A-D which represent 90° intervals of the rotation of shaft 12 it will be initially noted that drive pin 14 is at one extreme of slot 18-5, specifically the counterclockwise extreme in Figures 9 A-D. The illustrated counterclockwise rotation of shaft 12 causes drive pin 14 to rotate therewith engaging the counterclockwise end of slot 18-5 and driving eccentric rotor 18 in a counterclockwise direction. Because the axis E-E of outer cylindrical surface 18-1 is eccentric relative to axis F-F of bore 18-2 which is, in turn, coaxial with axis A-A of shaft 12 rotor 18 effectively reciprocates in bore 16-2 in a double action pumping accommodated by the pivoting of ring 16. This produces two pumping cycles per revolution of shaft 12. As described with respect to Figure 8, Figure 9A represents simultaneous suction and discharge strokes. Oil from sump 30 is supplied via groove 12-5 and bore 18-4 to chamber 32 while oil in chamber 34 is pumped via bore 18-3 and bore 12-8 to bore 12-6 from which it passes to the bearings, etc. Relative to Figure 9A, Figure 9B represents the completion of the suction and discharge processes taking place in Figure 9A. It will be noted that bores 18-3 and 18-4 are effectively blocked by the walls of bore 16-2. Further counterclockwise rotation of shaft 12 and rotor 18 from the Figure 9B position will establish communication between the trapped volume defined by chamber 32 and bore 18-3 permitting the discharge of the oil in trapped volume 32 via bore 18-3, bore 12-8 and bore 12-6 for distribution to the parts requiring lubrication. Figure 9C is like Figure 9A except for the reversing of the functions of chamber 32 and chamber 34 which function as suction and discharge chambers, respectively. Figure 9D, like Figure 9B, represents the completion of the suction and discharge processes but for Figure 9C, not Figure 9A, and the trapped volume defined by chamber 34 will be communicated with bore 18-3 and discharged upon further counterclockwise rotation. A major advantage of the present invention is its operation upon reverse rotation of shaft 12. Figure 10 illustrates a position of reverse, clockwise, rotation. Upon clockwise rotation of shaft 12, pin 14 engages the clockwise end of slot 18-5 causing clockwise rotation of rotor 18. Under the conditions of clockwise rotation, as compared to counterclockwise rotation, bore 20-2 and groove 12-4 become the suction path and bore 18-4, bore 12-9 and bore 12-6 become the discharge path. Also, because slot 18-5 is about 45° in extent, the annular positions of the parts are different. Specifically comparing Figures 9C and 10 will locate pin 14 and bores 12-8 and 12-9 in the same positions but bores 18-3 and 18-4 are shifted 45° and Figure 10 is in an earlier stage of suction/discharge, i.e. it is about midway between Figures 9D and A in the cycle. Otherwise, pump assembly 10 will function the same in either direction of rotation. Although a preferred embodiment of the present invention has been illustrated and described, other changes will occur to those skilled in the art. For example, the Figures have been specific to a horizontal orientation of the compressor, but the present invention is suitable for vertical compressors also. Additionally, the pump need not be carried by a reduced diameter portion of the shaft 12, instead, bearing 22 can be enlarged to perform the function of shoulder 12-2. Also, grooves 12-4 and 12-5 may communicate with oil supply structure such as an annulus formed in bearing 22 and fed from a sump or oil supply, rather than communicating directly with the oil sump 30 via bores 20-2 and 20-3. Slot 18-5 need not be arcuate and could be replaced with a notch. It is therefore intended that the scope of the present invention is to be limited only by the scope of the appended claims.

Claims: A positive displacement pump (10) for a fluid machine having an oil supply comprising: a shaft (12) having a rotational axis (A-A); oil supply and distribution means (12-4, 12-5, 12-6, 12-8, 12-9); rotor means (18) drivingly received on said shaft and located eccentrically with respect to said rotational axis; means defining a cylinder (16) having a bore (16-2) defined by a pair of semicircular portions joined by straight sections corresponding in extent to a distance by which said rotor means is located eccentrically with respect to said rotational axis, said bore receiving said rotor means and coacting therewith to define at least one trapped volume (32, 34); oil passage means (18-3, 18-4) in said rotor means coacting with said oil supply and distribution means to supply oil from said oil supply to said trapped volume during a suction stroke and from said trapped volume to said oil distribution means during a discharge stroke; characterized in that said oil supply and distribution means (12-4, 12-5, 12-6, 12-8, 12-9) are formed in said shaft (12), said shaft has a limited relative rotational movement with respect to said rotor means and said means for supplying oil and said means for delivering oil each includes a pair of alternative flow paths (12-4, 12-5, 12-8, 12-9) whereby said pair of alternative flow paths for supplying oil from said oil supply to said trapped volume during a suction stroke and said pair of alternative flow paths for supplying oil from said trapped volume to said oil distribution means during a discharge stroke reverse function between paths of said pairs of alternative paths upon reverse rotation of said shaft. The pump according to claim 1, characterized in that two pumping cycles take place for each revolution of said shaft (12). The pump according to claim 1, characterized in that said rotor means (18) is drivingly received via a coaction between a slot (18-5) in said rotor means (18) and a pin (14) carried by said shaft (12). The pump according to claim 1, characterized in that said rotor means (18) has an eccentrically located bore (18-2) which receives said shaft (12). The pump according to claim 4, characterized in that said oil passage means in said rotor means (18) includes a pair of radially extending bores (18-3, 18-4). The pump according to claim 1, characterized in that said means defining a cylinder (16) pivots about a fixed point (B) responsive to rotation of said rotor means (18). The pump according to claim 1, characterized in that said oil supply means includes axial grooves (12-4, 12-5) in said shaft (12). The pump according to claim 1, characterized in that said oil distribution means includes radially extending bores (12-8, 12-9) in said shaft (12).

Inventors: PATTERSON DOUGLAS T, PATTERSON, DOUGLAS T.
Applicants: CARRIER CORP, CARRIER CORPORATION
Application year: 1994
Main classification: F04C2
IPC codes: F04B7, F04C2, F04C14